I think you make valid points, but as already said, it depends very much on the target audience.
In very general terms, it seems to me that there are three categories of historical book. Basic guides aimed at hobbyists, those aimed at the general reader and those aimed at the specialist. This, of course, does not necessarily exclude one category from the other
Take, for example, an Osprey publication aimed at the modeller or wargamer who, I would suggest, wants a short, handy reference and is unlikely to have the wherewithal or inclination to follow up individual references in obscure out of print publications or inaccessible archives, notwithstanding potential linguistic challenges. Such absence of footnotes or specific references does not, necessarily, make an Osprey a bad book, and are not really relevant to the usual reader who is looking for a 'one-stop shop'.
Take, however, a larger historical book, usually, though not always, a hard-back. Is this to be aimed at the general reader with a passing or general interest, and, thus, the potential for relatively large sales, or the specialist? The former, I would say, for much the same reasons as the Osprey reader, does not need detailed references, only general ones to give the reader (and publisher) a degree of confidence that the author has done his stuff conscientiously. The book need to be readable, entertaining as well as informative and, like the Osprey reader, they are not likely to want to follow up obscure references and illustrative evidence is usually included in the narrative. This does not mean, however, that such a book is bad history.
Turning now to the book aimed at the specialist. I would have thought that such a book, by the very nature of its target audience, will probably have limited appeal. It needs to be larger to accomodate the material and this must, I think, have implications on its price and its sales potential. If I am right, the corollary must also be difficulty in finding a publisher in the first place.
You and I, and probably large numbers of people who come to this forum, are numbered amongst the relatively few people who appreciate the detailed provenances and footnoted references of the specialist book.
I would, in closing, place a caveat. Footnoted references of the kind appropriate to specialist books does not necessarily make them good. At least one recent book has included footnoted references that were invented or clearly lifted from elsewhere (the archival references quoted had not existed for at approximately fifty years), and another included footnoted references that when checked did not say what the author pretended they did.